Tunnel sensor

ABSTRACT

A sensor ( 20, 100, 200, 300 ) for detecting the approach and exit of a vehicle ( 42 ) to a tunnel ( 46 ). In one embodiment there is a sensor ( 20, 100, 200, 300 ) with a photodiode ( 22   a ) that receives light through an inclined channel ( 30, 30′ ) or aperture ( 32, 332, 432 ). The channel provides a field of view ( 44, 344, 31 ) ahead and above the vehicle. The photosensor ( 22   a ) is thus sensitive to the change in light from this field of view ( 44, 344, 31 ) as a vehicle enters ( 46   a ) and exits ( 46   b ) a tunnel ( 46 ). Some embodiments of the present invention include a second photosensor ( 22   b ) with a wider field of view ( 112, 112″, 111 ) for detecting ambient light.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/065,987, filed Nov. 17, 1997, and to U.S. Provisional PatentApplication No. 60/076,854, filed Mar. 5, 1998. This applicationmincorporates herein by reference both of these provisional applicationsin their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for detecting a tunnel.More specifically, the apparatus relates to a photosensor for a vehiclefor detecting a tunnel.

Many vehicles include light sensors that actuate various systems of avehicle based upon ambient light conditions. For example, some sensorsprovide a signal that changes state as a result of the general level ofambient light. A controller receiving this signal actuates theheadlights on when the light level is low and off when the light levelis high. However, these sensors necessarily include sufficient filteringof the photosensor electrical signal and/or the response of thecontroller so as to not be sensitive to brief disturbances in ambientlight, such as shadows. Further, these sensors often include a ratherwide field of view and include light from ahead, behind, to either side,and from above the vehicle.

Yet another driving situation in which consumers find it desirable toactuate the headlights is the situation presented by the vehicleapproaching, within, and exiting a tunnel. Many drivers prefer to havetheir lights on when inside the tunnel and then turn the lights off asthe tunnel is exited. Conventional ambient light sensors have difficultyresponding to tunnels. The broad collection of light by suchconventional sensors makes them unresponsive to the tunnel until afterthe tunnel has been entered. Further, those sensors incorporating lowpass filtering or other time delays do not turn the headlights on untilafter the vehicle is well within the tunnel.

What is needed is a tunnel sensor that overcomes the disadvantages ofconventional sensors. The present invention does this in a novel andunobvious way.

SUMMARY OF THE INVENTION

One aspect of the present invention concerns an apparatus comprising aphotosensor, a housing, and a channel defined within the housing. Thephotosensor senses ambient light. The channel is generally inclinedabove the horizontal.

A different aspect of the present invention concerns a vehicle, such asa truck, bus, automobile, or motorcycle, and a housing mounted on saidvehicle. First and second apertures are defined within the housing. Aphotosensor receives ambient light from the second aperture. There isalso a channel defined within the housing for transmitting light to thephotosensor. A portion of the first aperture is above the secondaperture. The channel provides a field of view to the photosensor thatis above and ahead of the vehicle.

A different aspect of the present invention concerns an apparatus fordetecting a tunnel over a vehicle roadway. The method includes providinga channel in optical communication with a photosensor. The channel isoriented such that a portion of the channel generally faces ahead of thevehicle and generally faces above the vehicle. Light is permitted toenter the channel and fall incident upon the photosensor. A change inthe electrical characteristics of the photosensor is measured when thevehicle approaches a tunnel.

In a different aspect of the present invention, there is an apparatusfor a vehicle for sensing ambient light The apparatus includes ahousing. There is also a first photosensor with a first electricalcharacteristic and a second photosensor with a second electricalcharacteristic. There is a channel defined within the housing forproviding ambient light and a first field of view to the firstphotosensor. The second photosensor is provided ambient light from asecond field of view that is wider than the first field of view.

In a different aspect of the present invention, there is an apparatusfor detecting a tunnel over a roadway. The apparatus includes a vehiclefor travelling on the roadway. A housing is mounted on the vehicle.There is also a photosensor for sensing ambient light, the photosensorproviding a changeable electrical signal. A channel is defined withinthe housing for providing light to the photosensor. The channel isconstructed and arranged such that the electrical signal changes inresponse to the vehicle approaching a tunnel.

In a different aspect of the present invention, there is a vehicle withan actuatable air conditioning system or actuatable headlights. There isa housing mounted on the vehicle. The apparatus includes a firstphotosensor providing a first electrical signal. There is a channeldefined within the housing for providing ambient light in a first fieldof view to the first photosensor, the first field of view beinggenerally above and ahead of the vehicle. The apparatus includes acontroller for actuating the air conditioning system and/or theheadlights. The controller receiving the first electrical signal andactuating said air conditioning system and/or said headlights inresponse thereto.

In a different aspect of the present invention there is an apparatuswhich includes a vehicle having a front and a rear. A housing is mountedon the vehicle. There is an aperture defined within the housing. Theapparatus also includes a photosensor receiving ambient light from theaperture, the photosensor being mounted rearward of the aperture. Theaperture provides a field of view to the photosensor that is above andahead of the vehicle.

A different aspect of the present invention concerns a method fordetecting a tunnel over a vehicle roadway. The method includes providingan aperture an optical communication with a photosensor, the aperturebeing within a housing mounted on a vehicle. The aperture is oriented infront of the photosensor such that the aperture provides a field of viewto the photosensor that generally faces ahead of the vehicle andgenerally faces above the vehicle. Light is permitted to enter theaperture and fall incident upon the photosensor. A change is measured inthe electrical characteristics of the photosensor when the vehicleapproaches a tunnel.

Other aspects of the present invention will be apparent from thedescription of preferred embodiment, the claims, and the drawings tofollow.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional schematic of a first embodiment of thepresent invention.

FIG. 1B is a cross-sectional schematic of the apparatus of FIG. 1A astaken along line 1B—1B of FIG. 1A.

FIG. 2a is a side view of a vehicle incorporating one embodiment of thepresent invention.

FIG. 2b is a front elevational view of a vehicle incorporating oneembodiment of the present invention.

FIG. 3 is a pictorial representation of a vehicle incorporating oneembodiment of the present invention approaching, inside, and exiting atunnel.

FIG. 4A is a cross-sectional schematic of another embodiment of thepresent invention.

FIG. 4B is an enlargement of a portion of the channel of the apparatusof FIG. 4A.

FIG. 5 is a cross-sectional schematic of another embodiment of thepresent invention.

FIG. 6 is a perspective view of an apparatus according to anotherembodiment of the present invention.

FIG. 7 is a top plan view of the apparatus of FIG. 6.

FIG. 8 is a front elevational view of the apparatus of FIG. 6.

FIG. 9 is a cross-sectional view of the apparatus of FIG. 8 as takenthrough line 9—9 of FIG. 8.

FIG. 10 is a cross-sectional view of the apparatus of FIG. 8 as takenthrough line 10—10 of FIG. 8.

FIG. 11 is a schematic representation of an apparatus according toanother embodiment of the present invention.

FIG. 12 is a cross-sectional partial schematic representation of theapparatus of FIG. 9 as taken along line 12—12 of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the illustrated device, and such further applicationsof the principles of the invention as illustrated therein beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/065,987, filed Nov. 17, 1997, and to U.S. Provisional PatentApplication No. 60/076,854, filed Mar. 5, 1998. This applicationmincorporates herein by reference both of these provisional applicationsin their entirety.

The present invention relates to a sensor for a vehicle. The sensorprovides an electrical output signal that changes dependent upon whetherthe vehicle is approaching, within, or exiting a tunnel. The electricalsignal is provided to a controller that changes the state of a system ofthe vehicle. For example, if the vehicle is approaching a tunnel, thecontroller turns on the headlights of the vehicle preferably at orbefore the tunnel entrance and turns off the headlights at or near thetunnel exit. As another example, another controller can change thevehicle air conditioning to a recirculation mode within the tunnel so asto minimize the ingestion of polluted air within the vehicle. Those ofordinary skill in the art will recognize the application of the signalsfrom a tunnel sensor to control other vehicle systems that it isdesirable to actuate as a result of the vehicle entering a tunnel.

The present invention includes a photodiode that receives ambient lightthrough a channel and/or aperture defined within a housing. The channelor aperture has a preferably forward-facing field of view that isinclined relative to the horizontal such that the photodiode receiveslight from above and ahead of the vehicle. The field of view of thephotodiode is restricted so as to minimize light reaching the vehiclefrom directly above, behind, or from the sides of the vehicle. In otherembodiments, the present invention includes a second photosensor with afield of view wider than that of the first photosensor. The secondphotosensor preferably receives light from areas surrounding thevehicle, and not just the area in front and ahead of the vehicle, as isthe case with the first photosensor. The term horizontal as used hereingenerally refers to a plane defined by the roadway.

From a standpoint of cost and simplicity, it is preferable to have thetunnel sensor viewing aperture located in front of the photodiode, withthe radiation sensitive receiving of the photodiode facing toward theforward portion of the vehicle. However, those of ordinary skill in theart will recognize other photodiode placements and orientations thatpermit the photodiode to see an inclined forward view suitable fordetecting tunnels. For example, radiation received through the aperturecould be transmitted into a polished chamber which would reflect theradiation onto a photodiode in any orientation.

FIG. 1a is a cross-sectional schematic of a first embodiment of thepresent invention. Apparatus 20 includes a photosensor 22 within ahousing 24. Photosensor 22 may be of any type of sensor which has anelectrical characteristic in proportion to the incident of light uponthe photosensor. In one embodiment of the present invention photosensor22 is a silicon photodiode. Those of ordinary skill in the art willrecognize that other types of photosensors, including GAsP and GAPphotodiodes, are also useful with the present invention

One or more electrical wires 26 provide an indication of the change ofcharacteristics in photosensor 22 preferably to a circuit (not shown)that controls a system of a vehicle. The circuit may include a bufferamplifier, low pass filter, and a microprocessor. The circuit may be acombination of analog and digital components.

Photosensor 22 receives ambient light from a nearby aperture 28 definedin housing 24. Aperture 28 is at one end of a pathway or channel 30defined within housing 24. There is another aperture or opening 32 onthe other end of channel 30 that permits ambient light to enter opening32, travel through passageway 30, pass through aperture 28, and fallincident upon photosensor 22. Housing 24 is constructed from a materialthat is substantially opaque so as to only permit light entering pathway30 to fall incident upon photosensor 22. Although housing 24 is depictedas being constructed from a single piece, those of ordinary skill in theart will recognize that housing 24 can also be fabricated from multiplepieces.

Channel 30 includes an upper wall 34 and a lower wall 36. Upper wall 34is preferably inclined relative to the horizontal as indicated by angle38. Angle 38 is less than about 65 degrees. Lower wall 36 is preferablyinclined relative to the horizontal as indicated by angle 40. Angle 40is more than about two degrees above the horizontal. Although FIG. 1indicates a channel 30 in which walls 34 and 36 are angled relative toeach other, the present invention also contemplates a pathway 30 withparallel walls, and also contemplates cylindrical pathways and conicalpathways. Pathway 30 thus provides an inclined field of view betweenwalls 34 and 36 for photosensor 22. Housing 24 and channel 30 arepositioned within the vehicle such that photosensor 22 is provided afield of view through channel 30 that is generally above and ahead ofthe vehicle, so as to detect the change in light as a tunnel thresholdpasses through the field of view.

Photosensor 22 is in optical communication with pathway 30 and receivesincident radiation from a vertical field of view 44 which is inclinedupward as best seen in FIG. 2A. Referring again to FIG. 1A, A portion ofaperture 32 is located above aperture 28. Although the embodimentdepicted in FIG. 1 shows aperture 32 being larger than aperture 28, thepresent invention also contemplates apertures 32 and 28 being equal insize, and also embodiments in which aperture 28 is larger than aperture32.

FIG. 1B is a cross-sectional schematic of the apparatus of FIG. 1a astaken along line 1B—1B of FIG. 1A. Channel 30 preferably includes firstsidewall 33 and a second sidewall 35. Sidewalls 33 and 35 define anincluded angle 31 a between them. This angle is preferably between about2 degrees to about 90 degrees. Preferably angle 31 is about 40 degrees.Sidewalls 33 and 35 provide a horizontal field of view 31 b to sensor 22that is wide enough so as to see around dark objects, such as the backof a truck in front of vehicle 42, that would otherwise obscure the viewof sensor 22 and have the same effect as entering a tunnel.

As shown in FIG. 2b, field of view 31 b is preferably centered about thecenter line of vehicle 42. However, the present invention alsocontemplates those embodiments in which field of view 31 b is biasedtoward the left or the right of the vehicle. In some embodiments of thepresent invention field of view 31 b is biased to look toward the areaahead and left of the vehicle, accounting for the vehicle entering atunnel toward the right side of the tunnel. In other embodiments of thepresent invention angle 31 is biased to look toward the area ahead andright of the vehicle, accounting for the vehicle entering the tunneltoward the left side of the tunnel.

FIG. 2A is a side view of a vehicle incorporating one embodiment of thepresent invention. Apparatus 20 is preferably mounted on the dashboardof a vehicle 42 or near the rearview mirror mount. Although vehicle isshown represented as a car, the present invention is also useful ontrucks, busses, motorcycles, and other vehicles. Apparatus 20 isoriented such that pathway 30 generally faces toward the front of thevehicle and generally faces above the vehicle. Field of view 44 is showninclined above the horizontal by angle 40.

FIG. 3 is a pictorial representation of a vehicle incorporating oneembodiment of the present invention approaching, inside, and exiting atunnel. Vehicle 42 incorporating apparatus 20 is shown at position 50about 25 meters from entrance 46 a of a tunnel 46. When vehicle 42 is atposition 50, electrical signal characteristic 49 of photosensor 22 doesnot indicate that the vehicle is approaching a tunnel. Field view 44receives ambient light directly from the sky, or indirectly, such asfrom the surface of a hill or mountain. As vehicle 42 continuestravelling along pathway 43 in direction 48 and reaches point 52, whichis about 15 meters from entrance 46 a of tunnel 46, electricalcharacteristic 49 changes state, indicating that vehicle 42 isapproaching entrance 46 a of tunnel 46. This change in characteristic 49is measured by the circuit previously described. When vehicle 42 is atposition 52, field of view 44 is substantially filled by the uppersurface of tunnel 46.

As vehicle 42 continues in direction 48 and approaches position 54 andcrosses entrance 46 a of tunnel 46, field of view 44 continues to seegenerally the upper surface of tunnel 46, and electrical characteristic49 remains in the changed state. As vehicle 42 approaches point 56 about15 meters from exit 46 b of tunnel 46 along pathway 43 field of view 44begins to include portions of the sky outside of tunnel 46. In responseto the change in ambient light within field of view 44, electricalcharacteristic 49 changes back to the state indicating that vehicle 42is not within a tunnel. In some embodiments of the present invention,the headlights are turned off as the vehicle crosses exit 46 b. Althoughspecific distances have been shown and described, those of ordinaryskill in the art will recognize that by appropriate changes in theinclination of pathway 30, or the amplification applied tocharacteristic 49, or by means of appropriate filtering ofcharacteristic 49, the present invention can be made to turn headlightson and off at a variety of distances relative to the thresholds oftunnel 46, entrance 46 a and exit 46 b.

One embodiment of the present invention includes an electrical circuitthat measures the change in electrical characteristics of thephotosensor when the vehicle approaches a tunnel and when a vehicleleaves a tunnel. In this embodiment the electrical circuit would turn onthe headlights of vehicle 42 at about point 52 where field of view 44begins to be substantially filled with the upper surface of tunnel 46.The headlights of vehicle 42 would thus be turned on prior to theentrance into tunnel 46. Also, the electrical circuit can incorporate afilter or a delay such that the headlights remain on even thoughelectrical characteristic 49 has changed state at point 56, at whichpoint field of view 44 begins to see past the exit of tunnel 46. Thus,in some embodiments the headlights of vehicle 42 would remain on eventhough characteristic 49 indicates that field of view 44 does not see atunnel.

In another embodiment of the present invention, there is an electricalcircuit that places the air conditioning system in a recirculating modewhen the vehicle is within a tunnel. Thus, air within the vehicle couldbe recirculated prior to entering the tunnel, thus minimizing theingestion within vehicle 42 of polluted air within tunnel 42. In thisembodiment, the air conditioner is returned to a non-recirculating modeas vehicle 42 approaches the exit of the tunnel, or has left the tunnel.

FIG. 4a a cutaway of a schematic representation of another embodimentthe present invention. FIG. 4b is a closeup of a portion of a channelfrom FIG. 4A. Apparatus 100 includes photosensors 22 a and 22 b locatedon opposite sides of a circuit card 102. The electrical lead wires forphotosensors 22 are carried along circuit card 102. Circuit card 102preferably includes various buffer amplifiers, filters, and digitaldevices to process the outputs of photosensors 22.

Ambient light enters first opening 32, travels through passageway 30′and second opening 28, and falls incident upon photosensor 22 a.Passageway 30′, defined within housing 24′, includes an upper wall 34,lower wall 36, and sidewalls 33 and 35. The present invention alsocontemplates a channel 30′ with parallel walls, and also contemplatescylindrical pathways and conical pathways. Ambient light also passesthrough diffuser 104 and falls incident upon second photosensor 22 b. Asubstantially translucent or transparent cap 106 provides light to bothaperture 32 and diffuser 104, and also protects the components locatedtherein. In one embodiment of the present invention, diffuser 104 isgenerally hemispherical in shape, and provides a generally hemisphericalfield of view 112 to photosensor 22 b. However, diffuser 104 isoptional, and some embodiments of the present invention do not include adiffuser to provide light to photosensor 22 b.

Photosensor 22 a, which has light directed to it by passageway 30′,responds in a manner like that of photosensor 22 of apparatus 20,including the detection of tunnels ahead of a vehicle. In someembodiments of the present invention channels 30 or 30′ incorporate aplurality of ridges or cogs 108 which are useful for reducing the amountof internal reflection of light on the internal walls of channels 30 and30′. However, other embodiments of the present invention includepolishing of the inner surfaces of channels 30 or 30′.

Apparatus 100 also includes photosensor 22 b for detecting the amount ofambient light present, and turning on the headlights of a vehicle 42 asdusk or darkness approaches. Filter diffuser 104 provides a field ofview 112 to photosensor 22 b, that is wider than the field of view ofphotosensor 22 a.

By incorporating both photosensors 22 a and 22 b in the same apparatus,it is possible to reduce the size and cost of apparatus 100 relative tothe size and cost of providing two separate sensors. In addition, theresponse from one of the photosensors can be used to modify the responseof the other photosensor. For example, the amount of light received byambient light photosensor 22 b can be used to modify the response oftunnel photosensor 22 a, thus making photosensor 22 a more sensitive orless sensitive as a function of the amount of ambient light.

Electrical signal characteristic 113 of FIG. 3 shows a response ofphotosensor 22 b as vehicle 42 drives toward, in, and out of tunnel 46.Because filter diffuser 104 provides wide field of view 112 to sensor 22b, there is little response by sensor 22 b to tunnel 46 until vehicle 42is relatively close to the entrance of tunnel 46, such as position 54.In the vicinity of the entrance to tunnel 46 electrical characteristic113 begins to change as increasing amounts of field of view 112 areexposed to the decreasing amounts of ambient light within tunnel 46.However, because of wide field of view 112 this change in electricalcharacteristic 112 does not occur at position 52.

In some embodiments of the present invention electrical characteristic113 can be modified to produce a signal that responds more slowly. Byway of example only, characteristic 113 could be provided to a low passfilter or to a timing circuit. The resultant signal, which is avariation of characteristic 113 that is less sensitive, could be used toturn on the headlights of vehicle 42, change the recirculation state ofthe air conditioner of vehicle 42, or effect some other system ofvehicle 42 sensitive to tunnels.

Characteristic 113 with or without a low pass filter or timing circuit,could be used to modify the system control circuitry which usescharacteristic 49 as an input. For example, the reduction incharacteristic 112 noted at position 54 could be logically ANDed withcharacteristic 49 at position 54 to turn on the headlights. In someembodiments of the present invention the combination of photosensors 22a and 22 b are useful for preventing the turn on of the vehicle'sheadlights when the vehicle is in a short tunnel or on a bridge. Forexample, the ability of photosensor 22 a to see ahead and above of thevehicle results in a change in electrical characteristic 49 when theexit of the tunnel is seen by sensor 22 a. This change can be used tooverride a headlight on signal which results from the simultaneousperception by sensor 22 b of the interior of the tunnel.

FIG. 5 is a cross-section of a schematic representation of a anotherembodiment of the present invention. Apparatus 200 includes photosensors22 a and 22 b located on circuit card 102″. Circuit card 102″ differsfrom circuit card 102 in that photosensors 22 a and 22 b are located onthe same side of circuit card 102″. Those of ordinary skill in the artwill recognize that the present invention also contemplates thosecircuit card arrangements in which photosensor 22 b is located on aseparate circuit card, and also those embodiments in which photosensor22 b has an angular inclination relative to photosensor 22 a.

Photosensor 22 a receives ambient light directed through a pathway 30″within housing 24″ in a matter as previously described. Circuit card 102also includes a photosensor 22 b which receives ambient light through afilter diffuser 104″ in a manner as previously described. A cap 106″provides protection for elements of apparatus 200 located therein.Apparatus 200 differs from apparatus 100 in that field of view 112″ isgenerally in the same direction as field of view 44, and that field ofview 112″ is less than field of view 112. Field of view 112″ is at leastabout a quarter of a spherical view.

FIGS. 6-12 depict another embodiment of the present invention. Externalviews of an apparatus 300 are shown in FIGS. 6-8. Apparatus 300incorporates a first photodiode 22 a constructed and arranged so as todetect tunnel thresholds in a first, narrower field of view andphotodiode 22 b for detecting ambient light in a second, wider field ofview. Apparatus 300 includes a cover 306 which is generally transparentto the radiation of interest, a housing 324, and a rear body 380.Apparatus 300 is generally arranged so as to be placed in an automobilenear the rearview mirror of the front windshield. Cover 306 provides aview of the surroundings to photosensors 22 a and 22 b through thewindshield. Those of ordinary skill in the art will recognize theconstruction, arrangement, and placement of apparatus 300 in otherpositions of a vehicle such that a view of approaching tunnel thresholdsand surrounding ambient light is provided.

FIGS. 9 and 10 depict cross-sectional views of apparatus 300 throughlines 9—9 and 10—10, respectively, of FIG. 8. As best seen in FIG. 9,second photosensor 22 b is mounted to a circuit card 302. Circuit card302 includes types of circuitry as described for circuit card 102. Lightpassing through cover 306 and hemispherical diffuser 104 falls incidentupon photosensor 22 b, resulting in an electrical signal therefrom.Diffuser 104 provides a field of view 112 that is generally broader thanthe field of view provided to photodiode 22 a in both azimuth andelevation.

The output of photosensor 22 b is used as both a solar sensor and atwilight sensor. The electrical output of photosensor 22 b is provided afirst amplification which results in a first amplified electrical signaland is used as a solar sensor. This first signal is provided, forexample, to the controller of the air conditioning system which uses thefirst amplified electrical signal for adjusting the heating or coolingof the passenger compartment of the vehicle. In one embodiment the firstamplification is a factor of about 3.7 million.

The first amplified signal is then provided a second amplification toresult in a second amplified signal which is the twilight signal 112 asdiscussed herein. This twilight signal is more amplified so as to permitdetection of lower levels of light. The second amplification is a factorof about 80 over the first amplification, for a total amplification ofabout 300 million. In a preferred embodiment of apparatus 300,electrical components for providing both the first amplification and thesecond amplification are attached to circuit card 302. A plurality ofpins 382 provide various electrical signals from circuit card 302 tovarious controllers of the vehicle.

FIG. 10 depicts a section of apparatus 300 showing first photosensor 22a. Photosensor 22 a is mounted to circuit card 302, where its electricalcharacteristics may be modified by various circuitry as described hereinfor circuit card 102. Electrical signals from photosensor 22 a areprovided to various controllers through pins 382.

Light received through an elevational field of view 344 and azimuthalfield of view 31 falls incident upon photosensor 22 a. A lower wall 336defined by housing 324 establishes a lower optical path inclinedrelative to the horizontal by angle 340. An accented edge 332 definedwithin housing 324 in conjunction with the upper edge of the receivingsurface of photodiode photosensor 22 a define an upper optical pathinclined relative to the horizontal by angle 338. Angles 338 and 340 arepreferably greater than about 2 degrees and preferably less than about65 degrees. In one most preferred embodiment angles 340 and 338 are eachabout 7 degrees, thus establishing the upper and lower optical paths asbeing approximately parallel. Upper wall 334, unlike wall 34 of channel30, does not limit field of view 344 beyond the limitation provided byaccented edge 332. Instead, upper wall 334 is approximately parallel tothe horizontal but may also be inclined away from the upper optical pathso as to not interfere therewith.

In one embodiment of the present invention, the distance from thereceiving surface of photosensor 22 a to corner 332 of upper wall 334 isabout 0.2 inches. The distance from corner 332 to lower wall 336 isabout 0.04 inches. The azimuthal viewing path, as best seen in FIG. 12,is defined by a minimum width of about 0.13 inches. The active receivingarea of photodiode 22 a is about 0.044 inches by 0.044 inches.

FIG. 12 is a partial schematic representation of a cross-section ofapparatus 300 as viewed from line 12—12 of FIG. 9. Photosensors 22 b and22 a are shown mounted generally side by side on circuit card 302.Hemispherical diffuser 104 provides light from an azimuthal field ofview 111 that is wider than the azimuthal field of view 31 ofphotosensor 22 a. Sidewalls 333 and 335 of housing 324 generallyestablish field of view 31. However, those of ordinary skill in the artwill recognize that a sidewall is not necessary to define the field ofview, provided that an accented edge or aperture is used. Photosensors22 b and 22 a are preferably optically isolated from each other andreceive incident radiation substantially from only their respectivefields of view.

FIG. 11 schematically represents yet another embodiment of the presentinvention. A photosensor 22 a is mounted to a circuit card 402 within ahousing 424. Photosensor 22 a receives radiation through a field of view444 established by the placement of sensor 22 a relative to an aperture432. The upper optical path is established by placing the upper edge ofaperture 432 at an angle 438 relative to the upper edge of the activereceiving area of sensor 22 a and relative to the horizontal. The loweroptical path is established by placing the lower edge of aperture 432 atan angle 440 relative to the lower boundary of the receiving area ofphotosensor 22 a and relative to the horizontal. Angles 438 and 440 arepreferably greater than about 2 degrees and preferably less than about65 degrees. Most preferably, angles 438 and 440 are about 7 degrees. Thedistance x from the receiving area of photosensor 22 a to the aperturein one preferred embodiment, is about 0.2 inches. The height h ofaperture 432 in that embodiment is about 0.044 inches. The width ofaperture 432 in that embodiment is about 0.13 inches. As seen in FIG.11, it is not necessary to have a channel to provide light from theouter aperture to the photosensor. By so inclining the lower and upperoptical paths, a portion of aperture 32 and 432 is above photosensor 22a.

For those embodiments having both photosensors 22 a and 22 b, the solarsignal or twilight signal from sensor 22 b can be used to modify theresponse of a vehicle system to the approach of a tunnel. For example,for ambient conditions of generally low light, the headlights of thevehicle can be made to turn on sooner than for a bright day. On a brightday the headlights would be actuated after a first period of time afterindication by tunnel sensor 22 a of a tunnel entrance. On a darker day,the headlights would be actuated after a second period of time afterindication by the tunnel sensor 22 a of a tunnel entrance, the secondperiod being shorter than the first period. Those of ordinary skill inthe art will be able to determine the appropriate difference between thefirst period and second period based on their understanding of theircustomers preferences.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

What is claimed is:
 1. An apparatus comprising: a photosensor forsensing ambient light; a housing; and a channel defined within saidhousing for providing light to said photosensor, said channel having anupper wall, a lower wall, and two sidewalls; wherein the lower wall isinclined more than about two degrees above the horizontal, the upperwall is inclined less than about sixty five degrees above thehorizontal, and the included angle between said sidewalls is more thanabout two degrees and less than about ninety degrees.
 2. The apparatusof claim 1, wherein said photosensor provides a first electrical signalin response to light from said channel, and which further comprises avehicle with actuatable lights and a controller, said controlleractuating said lights in response to said first electrical signal. 3.The apparatus of claim 2, wherein said first electrical signal changesin response to said vehicle approaching a tunnel and before said vehicleenters the tunnel.
 4. The apparatus of claim 2, wherein said vehicleincludes an actuatable recirculating air conditioning system, and saidair conditioning system recirculates in response to said firstelectrical signal.
 5. The apparatus of claim 2, which further includes asecond photosensor with a second electrical signal responsive to ambientlight received thereon, said second photosensor receiving light from asecond field of view that is at least one quarter of a spherical view,wherein said controller receives said first electrical signal and saidsecond electrical signal and actuates said lights in response thereto.6. The apparatus according to claim 5, wherein said channel providesambient light to said photosensor from above and ahead of said vehicle,and restricts ambient light to said photosensor from behind saidvehicle.
 7. The apparatus according to claim 1, wherein said channelprovides ambient light to said photosensor from above and ahead of saidvehicle, and restricts ambient light to said photosensor from behindsaid vehicle.
 8. The apparatus according to claim 7, wherein saidchannel provides a field of view to said photosensor that is biased toprovide more light from one of the left side of said vehicle or theright side of said vehicle and less from the other side of said vehicle.9. The apparatus according to claim 7, wherein at least one of saidwalls of said channel includes a plurality of ridges for reducingreflection of light.
 10. The apparatus according to claim 7, whereinsaid photosensor is a photodiode with a radiation receiving surface thatgenerally faces to the front of the vehicle.
 11. An apparatuscomprising: a vehicle; a housing mounted on said vehicle; a firstaperture defined within said housing; a second aperture defined withinsaid housing; a photosensor receiving ambient light from said secondaperture; and a channel defined within said housing for transmittinglight to said photosensor, said channel having a lower wall with aportion of said lower wall inclined more than about two degrees abovethe horizontal, said channel having two ends, said channel having saidfirst aperture at one end and said second aperture at the other end;wherein a portion of said first aperture is above said second aperture,and said channel provides a field of view to said photosensor that isabove and ahead of said vehicle.
 12. The apparatus according to claim11, wherein said photosensor provides a first electrical signal inresponse to light from the field of view, and which further comprises avehicle with actuatable lights and a controller, said controlleractuating said lights in response to said first electrical signal. 13.The apparatus of claim 12, wherein said vehicle includes an actuatablerecirculating air conditioning system, and said air conditioning systemrecirculates in response to said first electrical signal.
 14. Theapparatus of claim 12, wherein said first electrical signal changes inresponse to said vehicle approaching a tunnel and before said vehicleenters the tunnel.
 15. The apparatus of claim 14, which further includesa second photosensor with a second electrical signal responsive toambient light received thereon, said second photosensor receiving lightfrom a second field of view larger than the first field of view, whereinsaid controller receives said first electrical signal and said secondelectrical signal and actuates said lights in response thereto.
 16. Theapparatus of claim 11, wherein said channel restricts ambient light tosaid photosensor from behind said vehicle.
 17. The apparatus of claim16, wherein said channel includes sidewalls, and the included anglebetween said sidewalls is more than about two degrees and less thanabout ninety degrees.
 18. A method for detecting a tunnel over a vehicleroadway, comprising: providing a channel in optical communication with aphotosensor, the channel being within a housing mounted on a vehicle;orienting the channel such that a portion of the channel generally facesahead of the vehicle and generally faces above the vehicle; restrictinglight to the photosensor from behind the vehicle; permitting light toenter the channel and fall incident upon the photosensor; and measuringa change in the electrical characteristics of the photosensor when thevehicle approaches a tunnel.
 19. The method according to claim 18,wherein said orienting provides a restricted field of view with a bottomthat is inclined at least about two degrees above the horizontal, andless than about sixty five degrees above the horizontal.
 20. The methodof claim 19, wherein said providing includes actuatable headlights forthe vehicle, and which further comprises responding to said measuring byactuating the headlights of the vehicle before the vehicle crosses athreshold of the tunnel.
 21. The method according to claim 18, whereinsaid providing includes actuatable headlights for the vehicle, and whichfurther comprises responding to said measuring by actuating theheadlights of the vehicle before the vehicle crosses a threshold of thetunnel.
 22. The method of claim 21, wherein the vehicle includes anactuatable recirculating air conditioning system, and, which furthercomprises recirculating the air conditioning system in response to saidmeasuring.
 23. An apparatus for a vehicle for sensing ambient light,comprising: a housing; a first photosensor with a first electricalsignal in response to ambient light incident thereon; a channel definedwithin said housing for providing ambient light in a first field of viewto said first photosensor; and a second photosensor with a secondelectrical signal in response to ambient light incident thereon, saidsecond photosensor being provided ambient light in a second field ofview, the second field of view being larger than the first field ofview; wherein said channel provides a field of view to said firstphotosensor that is generally above and ahead of said vehicle.
 24. Theapparatus of claim 23 wherein said second field of view is generallyhemispherical.
 25. The apparatus of claim 23 wherein said second fieldof view is at least one quarter of a spherical view.
 26. The apparatusaccording to claim 25, which further comprises a vehicle with actuatablelights and a controller, said controller actuating said lights inresponse to said first electrical signal, wherein said first electricalsignal changes in response to said vehicle approaching a tunnel andbefore said vehicle enters the tunnel.
 27. The apparatus according toclaim 19, which further comprises a vehicle with actuatable lights and acontroller, said controller actuating said lights in response to saidfirst electrical signal and said second electrical signal.
 28. Theapparatus according to claim 27, wherein said first electrical signalchanges in response to said vehicle approaching a tunnel and before saidvehicle enters the tunnel.
 29. The apparatus according to claim 27,wherein said vehicle includes an actuatable recirculating airconditioning system, and said air conditioning system recirculates inresponse to said first electrical signal and said second electricalsignal.
 30. The apparatus according to claim 27, wherein said channelrestricts ambient light to said first photosensor from behind saidvehicle.
 31. The apparatus according to claim 30, wherein said channelincludes a lower wall, and said lower wall is inclined more than abouttwo degrees above the horizontal.
 32. The apparatus according to claim31, wherein said channel provides a first field of view to saidphotosensor that is biased to provide more light from one of the leftside of said vehicle or the right side of said vehicle and less from theother side of said vehicle.
 33. An apparatus for detecting a tunnel overa roadway, comprising: a vehicle for travelling on the roadway; aphotosensor for sensing ambient light, said photosensor providing achangeable electrical signal in response to the ambient light; a housingmounted on said vehicle; and a channel defined within said housing forproviding ambient light to said photosensor, said channel having twoside walls and a lower wall; wherein the lower wall is inclined abovethe horizontal, and said side walls define an angle therebetween, andthe angle is greater than about two degrees and less than about ninetydegrees, and said electrical signal changes in response to said vehicleapproaching the tunnel.
 34. The apparatus according to claim 33, whereinsaid vehicle includes actuatable lights and which further comprises acontroller, said controller actuating said lights in response to thechange in said electrical signal.
 35. The apparatus according to claim34, wherein said channel defines a first field of view, and whichfurther includes a second photosensor with a second changeableelectrical signal in response to ambient light, said second photosensorreceiving ambient light from a second field of view larger than thefirst field of view, wherein said controller receives said firstelectrical signal and said second electrical signal and actuates saidlights in response thereto.
 36. The apparatus of claim 35, wherein saidsecond field of view is at least one quarter of a spherical view. 37.The apparatus of claim 34, wherein said channel provides ambient lightto said photosensor from above and ahead of said vehicle, and restrictsambient light to said photosensor from behind said vehicle.
 38. Anapparatus for a vehicle for sensing ambient light, comprising: a vehiclewith actuatable headlights; a housing mounted on said vehicle; a firstphotosensor providing a first electrical signal responsive to ambientlight received thereon; an aperture defined within said housing forproviding ambient light in a first field of view to said firstphotosensor, the first field of view being generally above and ahead ofsaid vehicle, the first field of view restricting light to said firstphotosensor from behind said vehicle, the field of view having a topinclined less than about sixty five degrees above the horizontal; and acontroller for actuating said headlights, said controller receiving saidfirst electrical signal and actuating said headlights in responsethereto.
 39. The apparatus of claim 38 wherein said first electricalsignal changes in response to said vehicle approaching a tunnel andbefore said vehicle enters the tunnel.
 40. The apparatus of claim 39,wherein said vehicle includes an actuatable recirculating airconditioning system, and said air conditioning system recirculates inresponse to said first electrical signal.
 41. The apparatus of claim 38which further includes a second photosensor with a second electricalsignal, said second photosensor receiving light from a second field ofview larger than the first field of view, wherein said controllerreceives said first electrical signal and said second electrical signaland actuates said headlights in response thereto.
 42. The apparatus ofclaim 38, wherein the field of view through said aperture has a bottom,and the bottom is inclined at least about two degrees above thehorizontal and less than about sixty five degrees above the horizontal.43. The apparatus of claim 42, wherein said first photosensor is aphotodiode with a radiation receiving surface that generally faces tothe front of the vehicle.
 44. The apparatus according to claim 43, whichfurther includes a second photosensor with a second electrical signalresponsive to ambient light received thereon, said second photosensorreceiving light from a second field of view larger than the first fieldof view, wherein said controller receives said first electrical signaland said second electrical signal and actuates said headlights inresponse thereto.
 45. The apparatus of claim 44, wherein the secondfield of view is at least one quarter of a spherical view.
 46. Anapparatus comprising: a vehicle having a front and a rear; a housingmounted on said vehicle; an aperture defined within said housing; and aphotosensor receiving ambient light from said aperture, said aperturelimiting light received by said photosensor from the rear of saidvehicle; wherein said aperture provides a field of view to saidphotosensor that is above and ahead of said vehicle, and the field ofview through said aperture has a bottom and the bottom is inclined atleast about two degrees above the horizontal, and less than about sixtyfive degrees above the horizontal.
 47. The apparatus of claim 46 whereinthe field of view through said aperture has a bottom and the bottom isinclined at least about two degrees above the horizontal, and less thanabout sixty five degrees above the horizontal.
 48. The apparatusaccording to claim 47, wherein said aperture provides a field of view tosaid photosensor that is biased to provide more light from one of theleft side of said vehicle or the right side of said vehicle and lessfrom the other side of said vehicle.
 49. The apparatus of claim 47,wherein said photosensor provides a first electrical signal in responseto light from the field of view, and which further comprises a vehiclewith actuatable lights and a controller, said controller actuating saidlights in response to said first electrical signal, and wherein saidfirst electrical signal changes in response to said vehicle approachinga tunnel and before said vehicle enters the tunnel.
 50. The apparatus ofclaim 46, wherein said photosensor provides a first electrical signal inresponse to light from the field of view, and which further comprises avehicle with actuatable lights and a controller, said controlleractuating said lights in response to said first electrical signal. 51.The apparatus according to claim 50, wherein said first electricalsignal changes in response to said vehicle approaching a tunnel andbefore said vehicle enters the tunnel.
 52. The apparatus according toclaim 50, wherein said vehicle includes an actuatable recirculating airconditioning system, and said air conditioning system recirculates inresponse to said electrical signal.
 53. The apparatus according to claim50, which further includes a second photosensor with a second electricalsignal responsive to ambient light received thereon, said secondphotosensor receiving ambient light from a second field of view largerthan the first field of view, wherein said controller receives saidfirst electrical signal and said second electrical signal and actuatessaid lights in response thereto.
 54. The apparatus of claim 53, whereinthe second field of view is at least one quarter of a spherical view.55. A method for detecting a tunnel over a vehicle roadway, comprising:providing an aperture in optical communication with a photosensor, theaperture being within a housing mounted on a vehicle with actuatableheadlights; orienting the aperture in front of the photosensor such thatthe aperture provides a field of view to the photosensor that generallyfaces ahead of the vehicle and generally faces above the vehicle;permitting light to enter the aperture and fall incident upon thephotosensor; measuring a change in the electrical characteristics of thephotosensor when the vehicle approaches a tunnel; and responding to saidmeasuring by actuating the headlights of the vehicle before the vehiclecrosses a threshold of the tunnel.
 56. The method of claim 55 whereinsaid orienting provides a restricted field of view with a bottom that isinclined at least about two degrees above the horizontal, and less thanabout sixty five degrees above the horizontal.
 57. The method accordingto claim 56, which further comprises restricting light to thephotosensor from behind the vehicle.
 58. The method The apparatusaccording to claim 57, wherein said providing includes an actuatablerecirculating air conditioning system for the vehicle, and which furthercomprises responding to said measuring by recirculating the airconditioning system of the vehicle before the vehicle crosses athreshold of the tunnel.
 59. The method The apparatus of claim 55, whichfurther comprises restricting light to the photosensor from behind thevehicle.
 60. An apparatus for a vehicle for sensing ambient light,comprising: a housing with a front and a rear; a first photosensorproviding a first electrical signal in response to ambient lightincident thereon; an aperture defined within said housing for providingambient light in a first field of view to said first photosensor; and asecond photosensor providing a second electrical signal in response toambient light incident thereon, said second photosensor being providedambient light in a second field of view, the second field of view beinglarger than the first field of view; wherein said aperture provides afirst field of view to said first photosensor that is generally aboveand ahead of the housing and inclined above the horizontal.
 61. Theapparatus of claim 60 wherein the first field of view has a bottom andthe bottom is inclined more than about two degrees above the horizontaland the first field of view has a top and the top is inclined less thanabout sixty five degrees above the horizontal.
 62. The apparatus ofclaim 61 which further comprises a diffuser for providing light to saidsecond photosensor.
 63. The apparatus according to claim 62 wherein saidfirst filed of view has a horizontal field of view that includes anangle of more than about two degrees and less than about ninety degrees.64. The apparatus according to claim 63 wherein said aperture is biasedto provide more light from one of the left side of said vehicle or theright side of said vehicle and less from the other side of said vehicle.65. The apparatus according to claim 63, wherein said first photosensoris positioned rearward of said aperture.
 66. The apparatus according toclaim 63 which further comprises a circuit card, wherein said firstphotosensor and said second photosensor are mounted to said circuitcard.
 67. The apparatus according to claim 63, wherein said housingincludes a plurality of ridges for reducing reflection of light in thefirst field of view.
 68. The apparatus according to claim 63 wherein thesecond field of view is at least one quarter of a spherical view. 69.The apparatus of claim 60 wherein the first field of view has a bottomand the bottom is inclined more than about two degrees above thehorizontal.
 70. The apparatus of claim 60 wherein the first field ofview has a top and the top is inclined less than about sixty fivedegrees above the horizontal.
 71. The apparatus according to claim 60wherein said aperture provides a horizontal field of view that includesan angle of more than about two degrees and less than about ninetydegrees.
 72. An apparatus for a vehicle for sensing ambient light,comprising: a vehicle with an actuatable recirculating air conditioningsystem; a photosensor providing an electrical signal responsive toambient light received thereon, said photosensor receiving light from afield of view generally above and ahead of said vehicle, the field ofview restricting light to said photosensor from behind said vehicle; anda controller receiving said electrical signal and capable of actuatingsaid recirculating air conditioning system in response thereto; whereinsaid electrical signal changes in response to a threshold of a tunnelpassing through the field of view, and said controller actuates saidsystem to recirculate before said vehicle crosses the threshold inresponse to the change in said electrical signal.
 73. The apparatusaccording to claim 72 wherein said vehicle includes actuatable lights,said controller is capable of actuating said lights, and said controlleractuates said lights in response to the change in said electricalsignal.
 74. The apparatus according to claim 72 wherein the field ofview to said photosensor is biased to provide more light from one of theleft side of said vehicle or the right side of said vehicle and lessfrom the other side of said vehicle.
 75. The apparatus of claim 72wherein the field of view has a bottom and the bottom is inclined morethan about two degrees above the horizontal.
 76. The apparatus of claim72 wherein the field of view has a top and the top is inclined less thanabout sixty five degrees above the horizontal.
 77. The apparatus ofclaim 72 which further includes a second photosensor providing a secondelectrical signal responsive to ambient light received thereon, saidsecond photosensor receiving light from a second field of view largerthan the first field of view, wherein said controller receives saidfirst electrical signal and said second electrical signal and actuatessaid system to recirculate in response thereto.
 78. An apparatus fordetecting a tunnel over a roadway, comprising: a housing with a frontand a rear, said housing defining an aperture; and a photosensorreceiving ambient light from said aperture, said aperture limiting lightreceived by said photosensor toward the rear of said housing; whereinsaid photosensor and said aperture are spaced apart such that saidaperture provides a field of view to said photosensor that is toward thefront of said housing and above said housing, the field of view throughsaid aperture has a bottom and the bottom is inclined at least about twodegrees above the horizontal, and less than about sixty five degreesabove the horizontal.
 79. The apparatus according to claim 78 whereinsaid photosensor has a horizontal field of view through said aperturethat includes an angle of more than about two degrees and less thanabout ninety degrees.
 80. The apparatus of claim 78 wherein the field ofview has a top, and the top is inclined less than about sixty fivedegrees above the horizontal.
 81. The apparatus according to claim 78,wherein said aperture provides a field of view to said photosensor thatis biased to provide more light from one of the left side of the roadwayor the right side of the roadway and less from the other side of theroadway.
 82. The apparatus according to claim 81, wherein saidphotosensor is positioned rearward of said aperture.
 83. The apparatusaccording to claim 82, wherein said housing includes a plurality ofridges for reducing reflection of light.
 84. The apparatus of claim 78,wherein said photosensor provides an electrical signal in response tolight from the field of view, and said electrical signal changes inresponse to the entrance of the tunnel moving into the field of view andbefore said housing passes through the tunnel entrance.
 85. Theapparatus according to claim 78, wherein said housing defines a secondfield of view, and which further includes a second photosensor receivingambient light through the second field of view, the second field of viewbeing larger than the first field of view.
 86. The apparatus accordingto claim 85 wherein the second field of view provides ambient light froma direction toward the front of said housing.
 87. The apparatusaccording to claim 86 wherein the second field of view is at least onequarter of a spherical view.
 88. A method for detecting a tunnel over avehicle roadway, comprising: providing an aperture in opticalcommunication with a photosensor, the aperture being within a housing;orienting the aperture such the aperture provides a field of view to thephotosensor which generally faces ahead of the housing and generallyfaces above the housing, the field of view being inclined above thehorizontal; restricting light to the photosensor from behind thehousing; permitting light to enter the aperture and fall incident uponthe photosensor; and providing a change in the electricalcharacteristics of the photosensor when the housing approaches a tunnel.89. The method according to claim 88, wherein said providing includes anactuatable recirculating air conditioning system for the vehicle, andwhich further comprises responding to the change in electricalcharacteristics by recirculating the air conditioning system of thevehicle before the vehicle crosses a threshold of the tunnel.
 90. Themethod according to claim 88, wherein said orienting provides a field ofview with a bottom that is inclined at least about two degrees above thehorizontal, and less than about sixty five degrees above the horizontal.91. The method of claim 88, wherein said providing includes actuatableheadlights for the vehicle, and which further comprises responding tothe change in electrical characteristics by actuating the headlights ofthe vehicle before the vehicle crosses a threshold of the tunnel.